Most of our DNA is non-coding or ‘junk’ DNA. As little as between 1% - 3% of our DNA is composed of the coding regions we call genes and the greatest quantity of non-coding DNA comes in the form of microsatellites.
Microsatellites are defined as short patterned non-coding regions containing specific genetic sequences that are repeated one right after the other (in direct sequence) within the genome of an organism. The repeated sequence in a microsatellite consists of two, three or four nucleotides (di-, tri-, or tetra-nucleotide repeats respectively) and can be repeated many times (upwards of 100).
During the analysis of microsatellites in humans and other organisms it has become evident that the number of repeated sequences in a particular microsatellite locus can vary (location on the chromosome). Thus one person may have a maternal chromosome microsatellite locus that contains three repeats while their paternal chromosome may have a microsatellite locus containing five tandem repeats.
Repeats larger than ten to fifteen iterations and without interruptions tend to be polymorphic. The number of repeats at a particular locus is highly polymorphic between individuals of the same species. This has been an extremely useful discovery for biologists as the microsatellite differences can, as a result, be used in DNA fingerprinting and paternal testing.
Web Resources On Microsatellite
What is a microsatellite?
Compound Microsatellite Repeats
Book Resources On Microsatellite
Microsatellites: Evolution and Applications by edited by David B. Goldstein, Christian Schlotterer
Snp and Microsatellite Genotyping by Ali Hajeer, Jane Worthington, Sally John